Pressure loaded gear pump

ABSTRACT

An improved pressure loaded pump having a flat sealing plate in the gear cavity with a face spaced from a parallel end face of the housing. A land member extends axially between the plate and housing in this area to surround the inlet and shaft openings on the plate and to define a pressure loading chamber. A seal pack in the chamber seals against the land member and one of the parallel seal plate and housing faces to separate the chamber from the inlet and shaft openings. The seal pack, in itself, further defines zones of pressure on the seal plate maintained at pressures different from that in the chamber.

.1 States. Patent 11 1 ifiinssunstolmsp GEAR PUMP,

Richard C.- Putnam, Hutchinson, V lfians.

Inventor:

Assignee: The Cessna Airc ralt Company,

Wichita, Kans,

Filed; ,A'pr. 9,1971 1 AWL 110.: 132,682 f Us. Cl. 418 /l 32, 4l 8/l351111'. c|...... 1 01c 19/08, F030 s/o0,1 =o4c 27/00.

Field of Search 418/131, 132, 133, 418/135 References cited- UNITEDSTATES PATENTS 2/1958 Compton 418/132 10/1967 418/131 .1 9 g 418/13211/1970 418/132 Ill 196 5 418/132 Petty .lohn et a1 Forsehher, Sissonet-al.

3,171,358 3/1965. Lauckfll, "418/132 3,363,5181/19611-'Si'sson,..L...'..;.L..., 41 132 Primary Examiner+Carlton R; CroyleAssistant Examiner-John .l. Vrablik Attorney-Gregory J. Nelson, James.W.- McFarland -.and Miller &' Brown [57 ABSTRACT I 7 Animprovedpressure loaded pump having a flat seal ing plate inthe gearcavity with a face spaced from a parallel end .taceof the housing. Aland'member'extends axially between the plate and housing in this area Ito surround the inlet and shaft openings on the plate and to define apressure loading'chambe r. A=seal pack in the-chamber seals against theland memberjandf'one of the parallel seal plate and housing faces'toseparate the chamber from the inlet and shaft'openings'Theseal pack,in-itself, further defines zones of pressure on'the seal platemaintained at pressures different from .that in' the chamber. 4'

' 12' Claims, 8 Drawing Figures 1 1 3,748, 063 1' 1451" July 24,1973:

Patented July 24, 1973 3,748,063

4 Sheath-Shoot 1 FIG. 2

INVENTOR RICHARD C. PUTNAM ATTORNEY Patented July 24, 1973 3,748,063

4 Sheets-Sheet z FIG. 3

INVENTOR RICHARD C. PUTNAM L/WW ATTORNEY Patented July 24, 19733,748,063

4 Sheets-Sheet U INVENTOR ZICHARDZUTNAM i ATTORNEY Patented July 24,1973 3,748,063

' 4 Shoots-Shoot 4 (D IO FIG. 7

INVENTOR UTNAM ATTORNEY 1 PRESSURE LOADED GEAR PUMP BACKGROUND OF THEINVENTION This invention relates to positive displacement hydraulic geardevices of the type incorporating pressure loaded side sealing plates.More particularly, the invention relates to improved sealing meanscontained wholly within the gear cavity effecting fluid sealing of thetransverse gear faces.

Devices of the class described generally incorporate a movable sealingplate arranged such that one side is pressed upon the transverse gearfaces to seal same. One or more pressure chambers, fed with fluid fromthe device, on the opposite side of the plate urge the plate toward thegears. Such chambers and the means required to seal the chambers havegenerally produced complicated and expensive design of the sealingplate, the housing and other components. In particular, prior artdesigns contemplate grooves in either the seal plate or the housing tocarry the sealing means delimiting and defining theradial limits of thepressure chamber.

SUMMARY OF THE INVENTION The present invention proposes improved sealingmeans providing pressure loaded sealing of the gear side facesdistinctly simpler and more economical than prior art. Yet, theinvention also creates precise side loading and optimal pump efficiency.It is particularly characterized by a lack of grooves in the seal plateand housings for delimiting the pressure chamber. Instead, the device ofthe present invention utilizes sealing meansfreely positioned withinthe-pressure chamber.

' The inventioncontemplates a flat sealing plate mov ably disposedwithin the gear cavity with one side adjacent the gear side faces andthe'outer face spaced from The chamber covers an area of the sealingplate face so as to create sufficient force to urge the plate into'lightsealing engagement with the lateral faces of the gears.

A three-element seal pack, disposed within the pressure chamber, sealsagainst one 'ofthe parallel faces and at right angles against the landto isolate the pressure chamber from the lower pressure inlet'and shaftareas. Theseal pack itself defines a fluid zone within the main pressurechamber which is isolated therefrom and maintained at a pressuresomewhat less thatthat of the main pressure chamber. The invention thusprovides a pressure loading chamber of desireddesign with separatepressure zones without introducing complicated design of the seal plateor housing.

The invention, therefore, generally contemplates improved side sealingmeans for hydraulic gear devices simple and economical in design.

The invention has a primary objective of providing a sealing plate forengagement with the gears in a rotary fluid machine having a pressureloaded rear surface spaced from a parallel housing surface with landmeans projecting axially therebetween to define a pressure loadingchamber and to surround areasof pressure different from that of theloading chamber. Sealing means positioned at right angles against theland and one of the parallel faces isolate and seal the pressure loadingchamber from the areas maintained at different pressure.

A further object is to provide improved sealing means for devicesconstructed in accordance with the preceding objective.

Yet another object is to provide such sealing means which define a zonewholly confined within the sealing means hydraulically isolated from themain pressure loading chamber and maintained at a pressure differentfrom that of the main chamber.

These and other objectives and advantages of the present invention arespecifically set forth in or will become apparent from the followingdetailed description and accompanying drawings of a preferred embodimentof the invention.

BRIEF DESCRIPTION OF THE In the drawings:

FIG. 1 is a transverse section of a gear ing the present invention; 1

FIG. 2 is a view taken along line 2-2 of FIG. 1;

FIG. 3 is a viewtaken along line 3-3 of FIG. 1 showing the seal plateface 43 which engages the sides of the gears;

pump embody- FIG. 4 is a view taken'along line 44 of FIG. 1 show-DESCRIPTION or THE PREFERRED EMBODIMENT The gear device in FIG. 1,designated generally by the numeral 20, has a housing including endplates 21 and 22 and a body 23 sandwiched between and secured to theplates 21, 22. Agearcavity 24 within the body, shown in'FIG. 2, acceptsa pair of intermeshing gears 25, 26 whose teeth'tips closely fit thecavity wall 27. Each gear is affixed'to a shaft 28, 29 that is mountedfor rotation within b'ushings30 provided in shaft bores in the endplates. A fluid inlet 31 and outlet 32 open into opposite sides ofcavity 24 and communicate with external ports in the housing fordelivery and discharge of fluid. v g

1 In the following description of operation, the unit will be consideredas a pump though it is equally useful as a motor. Upon rotation of shaft28 by an external engine, gear 25 drives gear 26, and fluid drawn inthrough inlet 31 .is trapped in the intertooth gear spaces andtransported around the cavity wall 27 to high pressure outlet 32. Whiletraveling around the periphery of the gear'cavity from inlet to outlet,pressure of the intertooth spaces gradually increases, this pressureincrease with rotation generally being referred to as the pump pressuregradient. The pressure gradient zone of the pump denotes those portionssubject to pressure which are intermediate inlet and outlet pressure. Asthe gear teeth engage in the central mesh area 33, fluid displaces anddischarges through the outlet. The higher pressure at the outlet sideurges the gears leftwardly in FIG. 2 so that the gear teeth tips sealagainst cavity wall 27 near the inlet to prevent efficiency reducingreverse flow from outlet to inlet around the gear periphery. The gearsthemselves effectively prevent leakage flow from outlet side 32 to inletside 31- through mesh area 33. The gear transverse faces 34 lightlypress and seal against end plate 21, and an axially movable seal plate36 disposed within the gear cavity 24 between gear faces 35 and flatface 45 of end plate 22 seals transverse face 35. Fluid pressure betweenthe seal plate and end plate urges seal plate 36 and the gearsleftwardly in FIG. 1 to effect sealing of the transverse gear faces.

As best seen in FIGS. 3 and 4, the outer periphery of seal plate 36closely fits cavity wall 27 about a substantial are from the inlet 31around each gear. Side 43 of the seal plate 36 is a flat surface ofbearing quality material that sealingly contacts gear faces 35. Reliefs37, 38 in the periphery of the plate adjacent the inlet and outletrespectively, interconnect the gear teeth pockets with inlet or outletto equalize pressure therewith as those pockets near inlet or outletduring gear rotation. Central openings 39, 40 acceptthe shafts, and agenerally circular depression 41 surrounds each opening as shown in FIG.3. Another recess 42 protrudes radially from each depression 41 past thegear root circle to communicate with the gear teeth pockets to feedpressure fluid to openings 39, 40 for lubrication of the shaft bushings.Recesses 42, positioned a short are distance fromrelief 37, directfairly low pressure fluid to the bushings as they pick up fluid at alower pressure point in the pump pressure gradient zone. To thoseskilled in the art, it will be apparent that pressure at a certainlocation in the pressure gradient zone, such as at depression 42,,variesmarkedly with changes in different operating parameters such as speed ofgear rotation and outlet pressure. Pressure in the bearing openingsaccordingly may vary from near inlet pressure to outlet pressure withchanges in the operating parameters. Bearing pressure may be controlled.if desired by, for instance, including a pressure relief valve in'thebearing pressure area.

The opposite face 44 of the seal plate extends in close association withend face 45. FIG. 4' illustrates seal plate face 44 and the upstandingland member 46 formed integrally :with seal plate 36 upon'face 44 andextending axially thereof toward end plate face 45.

'Land 46 surrounds each shaft opening 39, 40 and has a portion 47substantially surrounding the inlet by extending between the shaftopenings and from each opening 39, 40 laterally to the cavity wall 27.Note that in this embodiment a seal receiving groove 70 in portion 47extends around inlet 31 and opens at the cavity wall 27 on oppositesides of the inlet. As can be seen both in'FlGS. 3 and 4, the sealingplate has through oblong slots 48 permitting communication of fluid inthe intertooth pockets with face 44 as the pockets passslots 48. v

The outward edge 49 of land 46 forms, along with a portion of cavitywall 27, the periphery ofa fluid chamber 50 laterally bounded by theparallel spaced faces 44 and 45 of the sealing plate and end plate. Aportion of chamber 50 is occupied by a seal pack assembly 51 which willbe described in greater detail below. Pressure fluid is communicated tochamber 50 via the seal plate peripheral relief 38. Chamber 50 extendsfrom gear cavity wall 27 radially inwardly past the gear root circle atthe bottom of the gear teeth pockets, and extends circumferentiallyaround the gears from the outlet to points adjacent the inlet andincludes areas of surface 44 opposite areas of face 43 exposed topressured less than outlet pressure. Outlet pressure in chamber 50 willtherefore overbalance the lower pressures adjacent the inlet and insidethe gear root circle to push plate 36 against the gears. In particular,the plate 36 is overbalanced and pressed into sealing engagement atthose areas where sealing is most required, in the pressure gradientzone and aroundthe shaft openings 39 and 40.

For effective operation it will be apparent that chamber 50 must besealed from the lower pressure shaft openings 39, and inlet 31 in orderto maintain the higher outlet pressure in chamber 50 and to minimizeinefficient fluid leakage from chamber 50. The sealing plate itselfprovides a portion of this chamber 50 sealing by its peripheral contactwith cavity wall 27 and by its physical separation of chamber 50 fromthe gear cavity proper. Positioned within chamber 50 and supported byland 46, the seal pack 51 seals against its edge 49 and against endplate face to separate chamber from shaft openings 39, 40 and inlet 31.FIG. 5 illustrates the three, generally 3-shaped elements 52, 53, 54comprising the seal pack, that, as seen in FIGS. 1 and 6,assemble uponseal plate face 44. Thin protector gasket 52, of nylon or otherextrusionresistant material, is of a U-shaped cross-section with itsbottom face 55 lying directly upon seal plate face 44 and its legs 56,57 extending axially toward end plate face 45. At its ends, gasket 52has a continuous'inner wall 58 surrounding a through opening in thegasket.

The elastomer o-ring 53 is an endless pliable element of generallycircular cross-section which is doubled and positioned within theprotector gasket 52 in the same characteristic 3 form. O-ring 53 loopsaround gasket inner wall 58 at each endand creates a double strandrunning the remainder of the length of the protector gasket. FIGS. 6 and7 clearly show how the o-ring fits within gasket 52 at inner wall 58 andat other positions. Elastomers of a variety of cross-sections may beutilized; the o-ring is chosen in the present embodiment due to itsavailability and economy. Alternately, the elastomer can be integrallyformed as a single element with eyelets at either end looping walls 58.

The third seal element is a generally U-shaped backup gasket 54 made ofrelatively rigid fibrous material and generally conforming in' size andshape to the portion of seal flat face 44 forming the lateral face ofpressure chamber 50. As seen in FIG. 6, the protector gasket legs 56, 57fit within depending back-up gasket legs 59, 60 to enclose arectangularspace containing elastomer 53. Upper'surface 61 of back-up gasket 54sealingly engages end plate face 45, and side face 62 seals against wall49 of land 46. Gasket-54 thus provides two right angle faces 61, 62which effectively seal chamber 50 from the lower pressure inlet andshaft openings. At its ends, as seen both in FIGS. 5 and 7, back-upgasket 54 has an island projection 63 snugly protruding inside protectorgasket wall 58. In this area, the outer back-up gasket leg 59 is deletedand protector gasket wall 56 engages gear cavity wall 27.

The protector gasket inner wall 58 and back-up gasket island 63cooperate to form a separate pressure chamber 64 within but isolatedfrom the pressure chamber 50. Slot opening 48 feeds intermediatepressure fluid from the pressure gradient area of the gear cavity tochamber 64 which is accordingly maintained subject to the intermediatepressure. These portions exbers is well known in the art and a morecomplete dea scription may be found in U.S. Pat. No. 2,809,592 ofWendell E. Miller and Leonard H. Reimer. The efficacy of such stagedpressure chambers relates directly to the size of the gear pump; a largegear pump which has a greater extent of pressure gradient area has fargreater need of intermediate pressure loading chambers than do smallpumps. Larger displacement pumps may require a plurality of staged zonesat distinct pressures.

Chamber 64 communicates through bore 65 with recess 66 in the face 61 ofgasket 54'. Recess 66 is substantially equal to chamber 64 in area toassure a pressure balance across island 63 and prevent the accumulationof higher discharge pressure in recess 66 which would, under certainconditions, increase the pressure in chamber 64 to discharge pressure.

By forming chamber 64 entirely by and within the seal pack elements,design of seal plate 36 and end plate face 45 are simplified, therebyreducing costs while increasing unit reliability and life. Assemblyprocedures are also considerably simplified. In contrast, prior artpumps normally create an intermediate pressure chamber by an island suchas 63 integrallyformed upon eitherthe seal plate or end plate and acomplex groove system surrounding the island and carrying fluid seals.

As discussed, back-up gasket 54 serves primarily to seal at, rightangles against edge 49 of land 46 and the end plate face 45. Protectorgasket 52 assists in sealing but serves primarily to prevent extrusionof .flowing of the soft o-ring 53'from its proper position. Highprescertain circumstances it has been found advantageous to inducelateral compressing of the left strand of o-ring 53 in FIG. 7 betweenbody 23 and island 58, and in other applications it may be desirable toinclude lateral v compressment of the elastomer.

The utilization of an intermediate chamber 64 is optional, beingdependent upon the overall size of the pump. Without such chamber thedesign and elements of the seal pack may be varied considerably, subjectto the primary requirement that the seal pack effect right angle sealingagainst the end plate face and the support wall to isolate pressurechamber 50 from the inletand the shaft openings.

The design of seal pack 51 is such that it can be freely positioned inthe pressure chamber 50 and need not be confined within a groove in theseal plate 36 or end plate 22. Pressure in chamber 50 urges the sealpack against land edge 49 and end plate face and holds the seal pack inproper sealing position. Fluid flow patterns set up in chamber will notmove or wash out" the seal pack due to the relatively rigid nature ofthe outer sides of the seal pack, especially leg 59 of gasket 54 whichis laterally unsupported over an extensive area and particularlyunsupported at peripheral relief 38. In contrast, prior art designsincorporate the sealing means in a groove to give the required lateralsupport. Being freely positioned in pressure chamber 50 also distinctlysimplifies assembly of the seal pack into the unit.

Sealing groove 70 in the inlet portion 47 of support 46 accepts ano-ring 71, L-shaped back-up gasket 72 and protector gasket 73,illustrated in cross-section in FIG. 8. The back-up gasket 72 along witho-ring 7l effect the primary sealing against end plate face 45 and thewall 74 of groove 70 adjacent the inlet 31. This seals against fluidleakage from the higher pressure shaft openings to inlet 31 and preventsloss of bearing lubrication fluid. Protector gasket 73, like gasket 52,prevents extrusion of o-ring 71.

The specific embodiment described utilizes a support member 46 integralwith the seal pla'teand a seal pack dlsposed to seal against the endplate. It will be quite sure differentials across a soft element such asan o-ring mediate its double strand and seals this trough from thedischarge pressure of chamber 50. Trough 67, shown in dotted lines inFIG. 4, is not sealed from the intermediate chambers 64 and normallycarries chamber 64 pressure by communicating therewith between walls 58and islands 63. This trough, along with chamber 64 at intermediatepressure, adds with the higher discharge pressure across the remainderof face 44 to produce a precise force slightly and uniformlyoverbalancing the gear cavity forces to urge the seal plate into light,but sealing contact with gear faces. The o-ring also initiallycompresses axially to provide slight preloading to hold gaskets 52 and54 against faces 44 and 45.

For clarity the relative proportions of the sealing elements have beensomewhat distorted in FIGS. 6-8. Elastomer 53 compresses axially but notlaterally. In

apparent that such arrangement can be reversed with the land member madeintegral with the end plate and the seal pack sealingagainstseal plateface 44. As noted above, the present invention also contemplatesvariations in designs of the 'seal pack, for instance, deletion of theintermediate pressure chamber 64.To the extent that these and othervariations and changes do not depart from the scope and spirit of theinvention'as set forth in the appended claims, they are intended to beincluded within same.

Having described out invention with sufficient clarity such that thoseskilled in the art may construct, use and practice it, we claim:

1. In an axially pressure loaded gear pump having a housing enclosing aninternal gear cavity having fluid inlet and outlet means openingintoopposite sides of the cavity; a pair of intermeshing gears havingtransverse gear faces disposed in the cavity and affixed to axiallyextending shafts rotatively mounted in the housing; an axially movableseal plate disposed entirely within said cavity having one ,side insealing engagement with the transverse gear faces and an opposite flatface disposed parallel and spaced from a transverse end face of the gearcavity to define a space therebetween,

said plate having bores accepting the shafts, wherein the improvementcomprises:

a land member integral with said seal plate extending axially betweensaid parallel faces and occupying only that portion of said spacebetween the parallel faces surrounding the inlet and shaft bores, saidland member and the wall of said cavity defining a pressure chamber ofsubstantially uniform axial width in the remainder of said space;

means communicating outlet pressure to said pressure chamber to urgesaid plate toward the gears;

first relatively rigid U-shaped gasket member in said chamber having abase and a pair of axially extending legs depending from the base,pressure in said chamber urging one of said legs and said baserespectively into sealing engagement with said land member and said gearcavity end face to seal said chamber from said inlet and said shaftbores, said one leg of the gasket being laterally supported by said landmember while the other leg of said gasket is laterally unsupportedagainst said pressure in the chamber;

resilient endless o-ring positioned within said U- shaped gasket member;second gasket in said pressure chamber cooperating with said firstgasket and o-ring to form a zone within and isolated from said pressurechamber; and

an aperture in said seal plate directing pressure to said zone lowerthan pressure in said chamber.

2. In an axially pressure loaded gear pump having an axially movableside sealing plate wholly contained within the rotor cavity of the pumphousing, the rear face of said sealing plate and the adjacent housingend wall comprising the transverse faces of a fluid pressure chambertherebetween of substantially uniform axial width, said sealing plateand housing defining inner and outer axially extending radial walls ofsaid chamber; improved means for sealing said chamber,.comprising:

first and second gaskets disposed wholly within said chamber andcooperating with each other to define an enclosed space therebetween,said first gasket having adjacent right angle faces urged by chamberpressure into sealing engagement with one of said chamber transversefaces and said inner wall of said chamber;

said second gasket having a base urged by chamber pressure into sealingengagement with the other of said chamber transverse faces; and

a resilient elastomer positioned in said space and compressed betweensaid gaskets so as to urge same initially against said chambertransverse faces.

3. In a hydraulic gear device having a housing enclosing an internalgear cavity having spaced apart end walls, fluid inlet and outlet meansopening into opposite sides of the cavity; a pair of intermeshing gearsdisposed in said cavity between said end walls and closely fitting thecavity confines and presenting a transverse side spaced from an adjacentone of said end walls of the cavity; axially extending shafts in thehousing rotatively supporting each gear whereby upon rotation said gearscarry fluid from the inlet to the outlet; wherein the improvementcomprises:

a unitary fluid sealing plate movably disposed within said gear cavityintermediate said transverse side of the gears and said adjacent endwall, said sealing plate having one side in sealing engagement with saidtransverse side of the gears and an opposing face arranged parallel andspaced from said adjacent end wall defining a space therebetween;

a land member disposed within said space and extensive through only thatportion of said space which surrounds said shaft openings and the inlet,said land member engaging the edge of said gear cavity adjacent theinlet, whereby said land member and said gear cavity edge define apressure chamber of substantially uniform axial width in the remainingportion of said space between said adjacent end wall and said opposingface of the sealing plate;

sealing means movably disposed wholly within said pressure chamber andconforming generally in shape to the edge of the land member; and

means communicating said pressure chamber with said outlet wherebypressure from said outlet biases said sealing plate against saidtransverse side of the gears and urges said sealing means axially intoopposite sealing engagement with said adjacent end wall and saidopposing face of the sealing plate and transversely into sealingengagement with said land member to seal said pressure chamber from saidshaft openings and said inlet,

said sealing means including a first U-shaped gasket with a pair ofparallel legs extending perpendicularly and axially from a bottom facewhich is adjacent said adjacent end wall, said chamber pressure urgingsaid bottom face axially against said adjacent end wall and urging oneof said perpendicular axial legs transversely against said edge of theland member.

4. The device of claim 1 further including a groove in said land member,and second sealing means in said groove preventing fluid flow acrosssaid land member between said shaft openings and the inlet.

5. The device of claim 1 wherein said sealing means further includesresilient means contained within said U-shaped first gasket and axiallycompressed between said sealing plate and adjacent end wall.

6. The device of claim 5 wherein said sealing means includes a secondU-shaped gasket having a bottom face lying upon said sealing plate andhaving parallel legs axially extending within said first gasket legs,said first and second gaskets forming therebetween a rectangular troughcontaining said resilient means.

7. The device of claim 6 wherein said resilient means comprise anendless elastomer o-ring located in said trough and surrounded by saidgaskets.

8. In an axially pressure loaded gear pump having a pair of intermeshinggears journalled upon axially extending shafts and located within ahousing pumping cavity, a fiat sealing plate in the housing cavity withone face in sealing engagement with the transverse gear faces and anopposite face parallel to and spaced from a transverse end face of thehousing cavity, and a rigid land member on said sealing plate extendingaxially in said space between the sealing plate and housing end plate todefine a pressure loading chamber of substantially uniform axial widthin said spacefed with outlet pressure fluid; improved means for sealingsaid chamber comprising:

a first U-shaped gasket having a back face with leg members depending atgenerally right angles thereto, said gasket disposed in said chamberhaving said back face and a leg member urged by pressure in said chamberinto sealing engagement at right angles with said land member and saidend plate;

a second U-shaped gasket inverted with respect to said first gasket andradially confined within the legs of said first gasket and having abottom face lyin'g upon the sealing plate to define a rectangular spacebetween said gaskets; and

a resilient elastomer member located inside said gaskets in saidrectangular space, said elastomer being compressed axially to initiallypreload said first and second gaskets against said end plate and sealingplate faces respectively.

9. The device of claim 8 wherein said resilient elastomer is an endlesselastomer o-ring arranged to form a double strand in said rectangularspace.

10. The device of claim 9 wherein said second gasket is provided withinterior walls extending into said rectangular space defining openingsin said bottom face registering with corresponding conduits in said sealplate which communicate with pressure developed in the gear cavityintermediate inlet and outlet pressure, said first gasket having anisland portion at each end adapted to be received within said interiorwalls to define intermediate pressure zones between each of said islandsand the sealing plate, said o-ring sealing against said interior wallsto separate said zones from the pressure chamber, I

11. An axially pressure loaded positive displacement gear pumpcomprising:

a housing enclosing an internal gear cavity and having spaced aparttransverse end faces;

fluid inlet and outlet means opening into opposite sides of said cavity;

a pair of intermeshing gears in said cavity affixed to axially extendingshafts joumalled in the housing,

, said gear peripheries closely fitting the wall of said cavity suchthat the gears receive low pressure fluid fromthe inlet anddeliverhigher pressure fluid at L the outlet, said gears having transversefaces spaced from an adjacent end face of said housing;

a sealing plate movably disposed in said cavity with one side in sealingengagement with the transverse gears faces and an opposite flat faceparallel and spaced from said adjacent housing end face to define aspace therebetween, said plate having openings accepting said shafts;

a single land member integrally formed upon one of said parallel housingand sealing plate faces extend ing axially in said space toward theother of said parallel faces, said land member extensive through onlythat portion of the space between said parallel faces adjacent the inletand shaft opening s, said land member and gear cavity wall defining apressure loading chamber of substantially uniform axial width in theremainder of said space between said parallel faces that is separatedfrom the shaft openings and inlet by said land member;

means communicating outlet pressure to said pressure loading chamber tourge the sealing plate into engagement with the transverse gear faces;

a sealing member in said pressure loading chamber partially encirclingsaid gears and having adjacent right angle faces urged into sealingengagement with said land member and said other of said parallel facesby pressure in said chamber to seal same from the inlet and shaftopenings, said sealing member having a groove opening toward the sealingplate; I

means in said land member sealing said shaft openings from the inlet;

a'second sealing member engaging the sealing plate and cooperating withsaid first mentioned sealing member to close said groove to form aninterior zone; and

elastomer means positioned in said zone for sealing said zone from saidpressure loading chamber.

12. The device of claim 11 wherein said sealing plate is provided withan aperture communicating pressure lower than said outlet pressure withsaid zone.

1. In an axially pressure loaded gear pump having a housing enclosing aninternal gear cavity having fluid inlet and outlet means opening intoopposite sides of the cavity; a pair of intermeshing gears havingtransverse gear faces disposed in the cavity and affixed to axiallyextending shafts rotatively mounted in the housing; an axially movableseal plate disposed entirely within said cavity having one side insealing engagement with the transverse gear faces and an opposite flatface disposed parallel and spaced from a transverse end face of the gearcavity to define a space therebetween, said plate having bores acceptingthe shafts, wherein the improvement comprises: a land member integralwith said seal plate extending axially between said parallel faces andoccupying only that portion of said space between the parallel facessurrounding the inlet and shaft bores, said land member and the wall ofsaid cavity defining a pressure chamber of substantially uniform axialwidth in the remainder of said space; means communicating outletpressure to said pressure chamber to urge said plate toward the gears; afirst relatively rigid U-shaped gasket member in said chamber having abase and a pair of axially extending legs depending from the base,pressure in said chamber urging one of said legs and said baserespectively into sealing engagement with said land member and said gearcavity end face to seal said chamber from said inlet and said shaftbores, said one leg of the gasket being laterally supported by said landmember while the other leg of said gasket is laterally unsupportedagainst said pressure in the chamber; a resilient endless o-ringpositioned within said U-shaped gasket member; a second gasket in saidpressure chamber cooperating with said first gasket and o-ring to form azone within and isolated from said pressure chamber; and an aperture insaid seal plate directing pressure to said zone lower than pressure insaid chamber.
 2. In an axially pressure loaded gear pump having anaxially movable side sealing plate wholly contained within the rotorcavity of the pump housing, the rear face of said sealing plate and theadjacent housing end wall comprising the transverse faces of a fluidpressure chamber therebetween of substantially uniform axial width, saidsealing plate and housing defining inner and outer axially extendingradial walls of said chamber; improved means for sealing said chamber,comprising: first and second gaskets disposed wholly within sAid chamberand cooperating with each other to define an enclosed spacetherebetween, said first gasket having adjacent right angle faces urgedby chamber pressure into sealing engagement with one of said chambertransverse faces and said inner wall of said chamber; said second gaskethaving a base urged by chamber pressure into sealing engagement with theother of said chamber transverse faces; and a resilient elastomerpositioned in said space and compressed between said gaskets so as tourge same initially against said chamber transverse faces.
 3. In ahydraulic gear device having a housing enclosing an internal gear cavityhaving spaced apart end walls, fluid inlet and outlet means opening intoopposite sides of the cavity; a pair of intermeshing gears disposed insaid cavity between said end walls and closely fitting the cavityconfines and presenting a transverse side spaced from an adjacent one ofsaid end walls of the cavity; axially extending shafts in the housingrotatively supporting each gear whereby upon rotation said gears carryfluid from the inlet to the outlet; wherein the improvement comprises: aunitary fluid sealing plate movably disposed within said gear cavityintermediate said transverse side of the gears and said adjacent endwall, said sealing plate having one side in sealing engagement with saidtransverse side of the gears and an opposing face arranged parallel andspaced from said adjacent end wall defining a space therebetween; a landmember disposed within said space and extensive through only thatportion of said space which surrounds said shaft openings and the inlet,said land member engaging the edge of said gear cavity adjacent theinlet, whereby said land member and said gear cavity edge define apressure chamber of substantially uniform axial width in the remainingportion of said space between said adjacent end wall and said opposingface of the sealing plate; sealing means movably disposed wholly withinsaid pressure chamber and conforming generally in shape to the edge ofthe land member; and means communicating said pressure chamber with saidoutlet whereby pressure from said outlet biases said sealing plateagainst said transverse side of the gears and urges said sealing meansaxially into opposite sealing engagement with said adjacent end wall andsaid opposing face of the sealing plate and transversely into sealingengagement with said land member to seal said pressure chamber from saidshaft openings and said inlet, said sealing means including a firstU-shaped gasket with a pair of parallel legs extending perpendicularlyand axially from a bottom face which is adjacent said adjacent end wall,said chamber pressure urging said bottom face axially against saidadjacent end wall and urging one of said perpendicular axial legstransversely against said edge of the land member.
 4. The device ofclaim 1 further including a groove in said land member, and secondsealing means in said groove preventing fluid flow across said landmember between said shaft openings and the inlet.
 5. The device of claim1 wherein said sealing means further includes resilient means containedwithin said U-shaped first gasket and axially compressed between saidsealing plate and adjacent end wall.
 6. The device of claim 5 whereinsaid sealing means includes a second U-shaped gasket having a bottomface lying upon said sealing plate and having parallel legs axiallyextending within said first gasket legs, said first and second gasketsforming therebetween a rectangular trough containing said resilientmeans.
 7. The device of claim 6 wherein said resilient means comprise anendless elastomer o-ring located in said trough and surrounded by saidgaskets.
 8. In an axially pressure loaded gear pump having a pair ofintermeshing gears journalled upon axially extending shafts and locatedwithin a housing pumping cavity, a flat sealing plate in the housingcavity with one face in sealing engagement witH the transverse gearfaces and an opposite face parallel to and spaced from a transverse endface of the housing cavity, and a rigid land member on said sealingplate extending axially in said space between the sealing plate andhousing end plate to define a pressure loading chamber of substantiallyuniform axial width in said space fed with outlet pressure fluid;improved means for sealing said chamber comprising: a first U-shapedgasket having a back face with leg members depending at generally rightangles thereto, said gasket disposed in said chamber having said backface and a leg member urged by pressure in said chamber into sealingengagement at right angles with said land member and said end plate; asecond U-shaped gasket inverted with respect to said first gasket andradially confined within the legs of said first gasket and having abottom face lying upon the sealing plate to define a rectangular spacebetween said gaskets; and a resilient elastomer member located insidesaid gaskets in said rectangular space, said elastomer being compressedaxially to initially preload said first and second gaskets against saidend plate and sealing plate faces respectively.
 9. The device of claim 8wherein said resilient elastomer is an endless elastomer o-ring arrangedto form a double strand in said rectangular space.
 10. The device ofclaim 9 wherein said second gasket is provided with interior wallsextending into said rectangular space defining openings in said bottomface registering with corresponding conduits in said seal plate whichcommunicate with pressure developed in the gear cavity intermediateinlet and outlet pressure, said first gasket having an island portion ateach end adapted to be received within said interior walls to defineintermediate pressure zones between each of said islands and the sealingplate, said o-ring sealing against said interior walls to separate saidzones from the pressure chamber.
 11. An axially pressure loaded positivedisplacement gear pump comprising: a housing enclosing an internal gearcavity and having spaced apart transverse end faces; fluid inlet andoutlet means opening into opposite sides of said cavity; a pair ofintermeshing gears in said cavity affixed to axially extending shaftsjournalled in the housing, said gear peripheries closely fitting thewall of said cavity such that the gears receive low pressure fluid fromthe inlet and deliver higher pressure fluid at the outlet, said gearshaving transverse faces spaced from an adjacent end face of saidhousing; a sealing plate movably disposed in said cavity with one sidein sealing engagement with the transverse gears faces and an oppositeflat face parallel and spaced from said adjacent housing end face todefine a space therebetween, said plate having openings accepting saidshafts; a single land member integrally formed upon one of said parallelhousing and sealing plate faces extending axially in said space towardthe other of said parallel faces, said land member extensive throughonly that portion of the space between said parallel faces adjacent theinlet and shaft openings, said land member and gear cavity wall defininga pressure loading chamber of substantially uniform axial width in theremainder of said space between said parallel faces that is separatedfrom the shaft openings and inlet by said land member; meanscommunicating outlet pressure to said pressure loading chamber to urgethe sealing plate into engagement with the transverse gear faces; asealing member in said pressure loading chamber partially encirclingsaid gears and having adjacent right angle faces urged into sealingengagement with said land member and said other of said parallel facesby pressure in said chamber to seal same from the inlet and shaftopenings, said sealing member having a groove opening toward the sealingplate; means in said land member sealing said shaft openings from theinlet; a second sealing mEmber engaging the sealing plate andcooperating with said first mentioned sealing member to close saidgroove to form an interior zone; and elastomer means positioned in saidzone for sealing said zone from said pressure loading chamber.
 12. Thedevice of claim 11 wherein said sealing plate is provided with anaperture communicating pressure lower than said outlet pressure withsaid zone.